Methods and apparatus for compensating for material distortion during additive manufacturing

ABSTRACT

Embodiments of the present disclosure are drawn to additive manufacturing methods. An exemplary method may include generating a tool path for forming a component via additive manufacturing, and assessing the tool path to identify a change in direction. The method may also include determining if the change in direction exceeds a predetermined angle, and adding a tangent arc to the tool path before the change in direction if the change in direction exceeds the predetermined angle.

TECHNICAL FIELD

Aspects of the present disclosure relate to apparatus and methods forfabricating components. In some instances, aspects of the presentdisclosure relate to apparatus and methods for fabricating components(such as, e.g., automobile parts, medical devices, machine components,consumer products, etc.) via additive manufacturing techniques orprocesses, such as, e.g., three-dimensional (3D) printing manufacturingtechniques or processes.

BACKGROUND

Additive manufacturing techniques and processes generally involve thebuildup of one or more materials, e.g., by layering, to make a net ornear net shape (NNS) object, in contrast to subtractive manufacturingmethods. Though “additive manufacturing” is an industry standard term(ASTM F2792), additive manufacturing encompasses various manufacturingand prototyping techniques known under a variety of names, including,e.g., freeform fabrication, 3D printing, rapid prototyping/tooling, etc.Additive manufacturing techniques may be used to fabricate simple orcomplex components from a wide variety of materials. For example, afreestanding object may be fabricated from a computer-aided design (CAD)model.

A particular type of additive manufacturing is more commonly known as 3Dprinting. One such process, commonly referred to as Fused DepositionModeling (FDM), comprises a process of melting a thin layer of aflowable material (e.g., a thermoplastic material), and applying thismaterial in layers to produce a final part. This is commonlyaccomplished by passing a continuous, thin filament of thermoplasticmaterial through a heated nozzle, which melts the thermoplastic materialand applies it to the structure being printed, building up thestructure. The heated material is applied to the existing structure inthin layers, melting and fusing with the existing material to produce asolid finished product.

The filament used in the aforementioned process is generally producedusing a plastic extruder, which may be comprised of a specially designedsteel screw rotating inside a heated steel barrel. Thermoplasticmaterial in the form of small pellets is introduced into one end of therotating screw. Friction from the rotating screw, combined with heatfrom the barrel, softens the plastic, which may be then forced underpressure through a small opening in a die attached to the front of theextruder barrel. This extrudes a string of material, which may be cooledand coiled up for use in the 3D printer.

Melting a thin filament of material in order to 3D print an item may bea very slow process, which may only be suitable for producing relativelysmall items or a limited number of items. As a result, the meltedfilament approach to 3D printing may be too slow for the manufacture oflarge items or a larger number of items. However, 3D printing usingmolten thermoplastic materials offers advantages for the manufacture oflarge items or a large number of items.

A common method of additive manufacturing, or 3D printing, generallyincludes forming and extruding a bead of flowable material (e.g., moltenthermoplastic), applying the bead of material in a strata of layers toform a facsimile of an article, and machining such facsimile to producean end product. Such a process is generally achieved by means of anextruder mounted on a computer numeric controlled (CNC) machine withcontrolled motion along at least the x-, y-, and z-axes. In some cases,the flowable material, such as, e.g., molten thermoplastic material, maybe infused with a reinforcing material (e.g., strands of fiber or othersuitable material or combination of materials) to enhance the material'sstrength.

The flowable material, while generally hot and pliable, may be depositedupon a substrate (e.g., a mold), pressed down or otherwise flattened tosome extent, and/or leveled to a consistent thickness, preferably bymeans of a compression roller mechanism. The compression roller may bemounted in or on a rotatable carrier, which may be operable to maintainthe roller in an orientation tangential, e.g., perpendicular, to thedeposited material (e.g., bead or beads of thermoplastic material). Theflattening process may aid in fusing a new layer of the flowablematerial to the previously deposited layer of the flowable material. Insome instances, an oscillating plate may be used to flatten the bead offlowable material to a desired thickness, thus effecting fusion to thepreviously deposited layer of flowable material. The deposition processmay be repeated so that successive layers of flowable material aredeposited upon an existing layer to build up and manufacture a desiredcomponent structure. When executed properly, the new layer of flowablematerial may be deposited at a temperature sufficient enough to allowthe new layer of such material to melt and fuse with a previouslydeposited layer, thus producing a solid part.

In some instances, the process of 3D-printing a part, which may utilizea large print bead to achieve an accurate final size and shape, mayinvolve a two-step process. This two-step process, commonly referred toas near-net-shape, may begin by printing a part to a size slightlylarger than needed, then machining, milling, or routing the part to thefinal size and shape. The additional time required to trim the part tofinal size may be compensated for by the faster printing process.

In the practice of the aforementioned additive manufacturing processes,some disadvantages have been encountered. In 3D printing, when a programencounters a corner or a substantial directional change in the toolpath, a row of deposited material may become distorted whentransitioning into a new direction. This occurs because by design, abead compression roller trails slightly behind an extrusion (ordeposition) nozzle. When executing a corner with little or no radius, acompression roller carrier-bracket must rotate behind the deposition (orextrusion) nozzle, in order to align itself in the new direction.Because of the offset between the roller and the nozzle, the compressionroller rotates completely off of the deposited bead, and is nowpositioned completely off the bead. When the extrusion nozzle begins tomove in the new direction, the roller re-engages the bead surface,pushing the soft material of the adjacent, newly deposited bead inward,distorting the shape of the newly compressed bead. This inward pullingof the material deforms the part, which may render the part unusable. Atthe present time, CNC additive manufacturing tool-path generatingsoftware may not have the capability of compensating for such distortionin a newly deposited bead of flowable material.

It is therefore desirable to provide systems and methods forcompensating for material distortion in additive manufacturingoperations.

SUMMARY

Aspects of the present disclosure relate to, among other things, methodsand apparatus for fabricating components via additive manufacturing,such as, e.g., 3D printing techniques. Each of the aspects disclosedherein may include one or more of the features described in connectionwith any of the other disclosed aspects.

Embodiments of the present disclosure are drawn to additivemanufacturing methods. An exemplary method may include generating a toolpath for forming a component via additive manufacturing, and assessingthe tool path to identify a change in direction. The method may alsoinclude determining if the change in direction exceeds a predeterminedangle, and adding a tangent arc to the tool path before the change indirection if the change in direction exceeds the predetermined angle.

In another embodiment, a method of performing additive manufacturing mayinclude generating a tool path. The method may further comprise moving anozzle of an additive manufacturing machine in a first direction of thetool path, wherein the nozzle is configured to deliver a heatedmaterial, and diverting the nozzle to form a tangent arc prior to achange in direction of the tool path in order to compensate for thechange in direction of the tool path. The method may further includemoving the nozzle in a second direction of the tool path, wherein thesecond direction is different than the first direction.

In one aspect, the disclosure describes, among other things, a systemand method to compensate for material pull-back (e.g., distortedthermoplastic material), which occurs when executing corners in a CNCadditive manufacturing program. An object of the present disclosure isachieved by modifying a characteristic of the deposited bead of aflowable material (e.g., thermoplastic material) to preemptivelycompensate for the anticipated material pull-back caused by reengagementof a compression roller during additive manufacturing. This isaccomplished by intentionally introducing a slight distortion into thetool path program, which results in the depositing of material in theopposite direction of the anticipated pull-back. This is accomplished byadding a tangent arc into the CNC tool-path, resulting in the tool pathdiverting slightly outward, and the material being deposited away fromthe normal tool path, just before the directional transition of theroller carrier occurs. When the material is pulled back inward, uponcontact with the compression roller, the added distortion will becancelled out as the material is pulled inward and settles into theproper location in the tool path. The programmed code for the tangentarc motion may be added into the proper sequence in the tool path at anypoint where an outside corner is to be executed. The code may be addedautomatically as the tool path is being generated by a computer aideddesign (CAD) software program or after generation of the tool path. Theprogram modification may also be added by manually modifying theprogram.

As used herein, the terms “comprises,” “comprising,” or any othervariation thereof, are intended to cover a non-exclusive inclusion, suchas a process, method, article, or apparatus. The term “exemplary” isused in the sense of “example,” rather than “ideal.”

It may be understood that both the foregoing general description and thefollowing detailed description are exemplary and explanatory only andare not restrictive of the disclosure, as claimed.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are incorporated in and constitute apart of this specification, illustrate exemplary aspects of the presentdisclosure and together with the description, serve to explain theprinciples of the disclosure.

FIG. 1 is a perspective view of an exemplary CNC machine operablepursuant to an additive manufacturing process in forming articles,according to an aspect of the present disclosure;

FIG. 2 is an enlarged perspective view of an exemplary carrier andapplicator assembly of the exemplary CNC machine shown in FIG. 1;

FIG. 3 is an enlarged cross-sectional view of an exemplary applicatorhead assembly shown in FIG. 2, during use;

FIG. 4a is a top view of a nozzle and a compression roller, depositingand compressing a new layer of flowable material following a normaltool-path in a first direction;

FIG. 4b is a top view of a nozzle and a compression roller, with thecompression roller positioned perpendicular to, and off of thepreviously-compressed bead to prepare for movement in a seconddirection;

FIG. 4c is a top view of a nozzle and compression roller, depositingmaterial in a direction different than the direction of the tool path ofFIG. 4a , and a resulting distortion in the newly deposited layer offlowable material;

FIG. 5a is a top view of a compression roller and a nozzle positioned ata right-angle to a newly-deposited bead of flowable material, a trailingedge of the bead having been distorted by intentional alteration of thetool path;

FIG. 5b is a top view of a compression roller and a nozzle and the addeddistortion from the altered tool path of FIG. 5a being cancelled out inthe corner of a turn as the compression roller and nozzle continue on inthe new direction different than the direction of the tool path of FIG.5a ; and

FIG. 6 is a flow-chart depicting steps of an exemplary method, accordingto an aspect of the present disclosure.

DETAILED DESCRIPTION

The present disclosure is drawn to, among other things, methods andapparatus for fabricating components via additive manufacturing or 3Dprinting techniques. More particularly, the methods and apparatusdescribed herein comprise a method for eliminating or reducingvariations or distortions in the flow path of deposited material whenchanging a direction of the tool path. For example, when a change indirection of the tool path exceeds a predetermined angle relative to thepreceding direction of the tool path, a compensatory movement (e.g., atangent arc) is added to the tool path program a predetermined distancein advance of the point of the directional change of the tool path. Indoing so, the tool path is diverted in an opposite direction relative tothe new change in direction by a predetermined amount. This addeddiversion of the tool path is then cancelled out during execution of thetool-path direction change.

For purposes of brevity, the methods and apparatus described herein willbe discussed in connection with the fabrication of parts fromthermoplastic materials. However, those of ordinary skill in the artwill readily recognize that the disclosed apparatus and methods may beused with any flowable material suitable for additive manufacturing,such as, e.g., 3D printing. CNC machine 1, shown in FIG. 1, includes abed 20 provided with a pair of transversely spaced side walls 21 and 22,a gantry 23 supported on one or more of side walls 21 and 22, carriage24 mounted on gantry 23, a carrier 25 mounted on carriage 24, anextruder 61, and an applicator assembly 43 mounted on carrier 25.Located on bed 20 between side walls 21 and 22 is a worktable 27provided with a support surface. The support surface may be disposed inan x-y plane, and may be fixed or displaceable along an x-axis or ay-axis. For example, in the displaceable version, worktable 27 may bedisplaceable along a set of rails mounted on bed 20. Displacement ofworktable 27 may be achieved using one or more servomotors and one ormore of rails 28 and 29 mounted on bed 20 and operatively connected toworktable 27. Gantry 23 is disposed along a y-axis, supported on sidewalls 21 and 22. In FIG. 1, gantry 23 is mounted on a set of guide rails28, 29, which are located along a top surface of side walls 21 and 22.Gantry 23 may either be fixedly or displaceably mounted, and, in someaspects, gantry 23 may be displaced along an a x-axis. In an exemplarydisplaceable version, one or more servomotors may control movement ofgantry 23. For example, one or more servomotors may be mounted on gantry23 and operatively connected to tracks, e.g., guide rails 28, 29,provided on the side walls 21 and 22 of bed 20.

Carriage 24 is supported on gantry 23 and is provided with a supportmember 30 mounted on and displaceable along one or more guide rails 31,32, and 33 provided on the gantry 23. Carriage 24 may be displaceablealong a y-axis on one or more guide rails 31, 32 and 33 by a servomotormounted on gantry 23 and operatively connected to support member 30.Carrier 25 is mounted on one or more vertically disposed guide rails 34and 35 supported on carriage 24 for displacement of carrier 25 relativeto carriage 24 along a z-axis. Carrier 25 may be displaceable along thez-axis by one or more servomotors mounted on carriage 24 and operativelyconnected to carrier 25.

As best shown in FIG. 2, mounted to carrier 25 is a positivedisplacement gear pump 74, which may be driven by a servomotor 75,through a gearbox 76. Gear pump 74 receives molten plastic from extruder60, shown in FIG. 1. A compression roller 59 for compressing materialmay be mounted on carrier bracket 47. Compression roller 59 may bemovably mounted on carrier 47, for example, rotatably or pivotablymounted. Compression roller 59 may be mounted relative to nozzle 51 sothat material, e.g., one or more beads of flowable material (such asthermoplastic resin), discharged from nozzle 51 is smoothed, flattened,leveled, and/or compressed by compression roller 59, as depicted in FIG.3. One or more servomotors 61 may be configured to move, e.g.,rotationally or pivotably displace carrier bracket 47 via a sprocket 56and drive-chain 65 arrangement.

With reference to FIG. 3, application head 43 may include a housing 46with a roller bearing 49 mounted therein. Carrier bracket 47 may bemounted, e.g., fixedly mounted, to an adaptor sleeve 50, journaled inbearing 49. As shown in FIG. 3, a bead of a flowable material 53 (e.g.,a thermoplastic material) under pressure from a source (e.g., one ormore extruder 60 and an associated polymer or gear pump) disposed oncarrier 25 may be flowed to applicator head 43, which may be fixedly (orremovably) connected to, and in communication with, nozzle 51. In use,flowable material 53 (e.g., thermoplastic material) may be heatedsufficiently to form a molten bead thereof, and may be extruded throughapplicator nozzle 51 to form multiple rows of deposited material 52 onto a surface of worktable 27. In some embodiments, flowable material 53may include a suitable reinforcing material, such as, e.g., fibers, thatfacilitate and enhance the fusion of adjacent layers of extrudedflowable material 53. In some aspects, flowable material 53 deliveredonto a surface of a worktable 27 may be free of trapped air, the rows ofdeposited material may be uniform, and/or the deposited material may besmooth. For example, flowable material 53 may be flattened, leveled,and/or fused to adjoining layers by any suitable means (e.g.,compression roller 59), to form an article.

Although compression roller 59 is depicted as being integral withapplicator head 43, compression roller 59 may be separate and discretefrom applicator head 43. In some embodiments, compression roller 59 maybe removably mounted to machine 1. For example, different sized orshaped compression rollers 59 may be interchangeably mounted on machine1, depending, e.g., on the type of flowable material 53 and/or desiredcharacteristics of the rows of deposited flowable material to be formedon worktable 27.

In an example, machine 1 may include a velocimetry assembly (or multiplevelocimetry assemblies) configured to determine flow rates (e.g.,velocities and/or volumetric flow rates) of deposited flowable material53 being delivered from applicator head 43. The velocimetry assembly maytransmit signals relating to the determined flow rates to theaforementioned controller coupled to machine 1, which then may utilizethe received information to compensate for variations in the materialflow rates.

In the course of fabricating a component, pursuant to the methodsdescribed herein, the control system of the machine 1, in executing theinputted program, would operate the several servomotors as described todisplace the gantry 23 along the x-axis, displace the carriage 24 alongthe y-axis, displace the carrier 25 along a z-axis, and/or rotatebracket 47 about the z-axis while nozzle 51 deposits flowable material53 and compression roller 59 compresses the deposited material. In anexample, compression roller 59 may compress flowable material 53 inuniform, smooth, rows of deposited material 52 to create an article, asshown in FIG. 3.

FIGS. 4a, 4b, and 4c , collectively, illustrate a nozzle 51 andcompression roller 59 for depositing and compressing, respectively, alayer of flowable material, and rotation of compression roller 59 whenthe tool path requires nozzle 51 to undergo a directional change inorder to form a printed part. FIG. 4a shows a layer of compressedflowable material 53 (e.g., a bead of compressed thermoplastic material)deposited along a normal tool path by nozzle 51 and compressed bycompression roller 59. As discussed above, compression roller 59 may beconfigured to rotate around nozzle 51 to execute a directional change ofthe tool path. FIG. 4b shows compression roller 59 rotated by 90-degreesso that a longitudinal axis of compression roller 59 is orientedparallel or substantially parallel to layer of compressed flowablematerial 53). In FIG. 4b , compression roller 59 is positioned off ofthe bead and is ready to proceed in a new direction, perpendicular tothe preceding tool path. Turning to FIG. 4c , as compression roller 59,following a normal tool-path, re-engages the newly deposited bead offlowable material, compression roller 59 advances, or pushes, soft orunhardened flowable material inward, which causes a distortion 63 in thenewly compressed flowable bead 53. This inward pulling of material maydeform the part, and may render the part unusable.

An objection of this disclosure is to compensate for this inward pullingof material during operation of machine 1 that may occur duringapplication and compression of beads of flowable material 53 during anon-linear portions of the tool path when forming an article. In orderto compensate for changes in direction of the tool path, withoutdeforming the deposited flowable material, a tangent arc 64, may beadded to the CNC tool-path program in the CAD programming software foreach directional change of the tool path that exceeds a predeterminedthreshold angle. In some instances, a tangent arc 64 may beautomatically added to the tool path, For example, a tangent arc 64 maybe added by CAD software, by tool-path software, and/or by externalsoftware. In other examples, a tangent arc 64 may be manually enteredinto the CAD programming software, tool-path software and/or externalsoftware. Exemplary software may include systems software and/orapplication software, which may be implemented by the machine computercontrol of machine 1.

In some aspects, tangent arc 64 may be added to the tool path while anearlier step of the tool path is being executed. For example, whilemachine 1 is executing a tool path and beginning to form a part, asoftware program monitoring the tool path may add a tangent arc 64 tothe tool path when an upcoming direction change in the tool path isdetected, in advance of that direction change. The program may analyzeupcoming direction changes in the tool path that are scheduled to occura predetermined amount of time in advance of their occurrence, so thatmodifications to the tool path may be made prior to the changes indirection to compensate for those direction changes. For example, aninterval of time (e.g., a buffer window) may be incorporated intotool-path monitoring programming to assess changes in tool-pathdirection in advance of the next steps for tool-path execution. Theinterval of time may be the same for different parts to be formed, ormay vary depending on one or more factors, for example, as a function ofthe final 3D part to be printed by machine 1 (e.g., a complex shaperequiring numerous changes in tool-path direction), and/or as a functionof the type of flowable material used during operation of machine 1(e.g., material properties of the flowable material, such as, viscosity,density, curing or hardening time of material, etc.).

In other aspects, one or more tangent arcs 64 may be added to a toolpath during generation of the tool path when a direction change is addedto the tool path, or one or more tangent arcs 64 may be added to thetool path after generation of the tool path and before the start ofexecution of the tool path by machine 1. For example, once a tool pathis generated, a program or a person coding the tool path mayautomatically or manually identify any changes in direction that mayrequire compensation and may add one or more tangent arcs 64 to the toolpath prior to those direction changes in order to compensate for thosedirection changes.

With reference to FIG. 5a , the intentionally distorted path of flowablematerial 53 is illustrated, with tangent arc 64. Tangent arc 64 is shownas an outward excursion of the path of flowable material 53 and isangled in a direction opposite to the direction of the upcomingdirection change. Tangent arc 64 is depicted at the end of the path offlowable material 53. A sub-routine in the CAD software (or othersuitable software) may insert tangent arc 64 prior to a point at whichthe directional transition will occur in the tool-path. By applyingtangent arc 64, the path of flowable material 53 is intentionallydiverted slightly outward, as shown in FIG. 5a , creating an intentionaloutward bulge.

Tangent arc 64 may be applied a certain distance ahead of a change indirection in the tool-path. This distance may be greater or lessdepending on the amount of direction change scheduled to occur in thetool path that will be compensated for. For example, tangent arc 64 maybe applied to the tool path at a greater or lesser distance if a greateror lesser change in direction in the tool path is to be compensated for,and/or a longer or shorter tangent arc 64 may be included. For example,when the tool path includes a corner having a smaller radius ofcurvature, the distance at which tangent arc 64 is applied may beadjusted accordingly. in some aspects, tangent arc 64 added to the toolpath may vary as a function of the type of corner, e.g., rounded orsquared, that is included in the tool path. In instances where a squarecorner is printed without compensation (e.g., applying tangent arc 64 tothe tool path), the resulting compressed flowable bead 53 shape tends tobe an arc canted inward, whose length is approximately equal to thelength of the compression roller 59. The amount of inward movement tendsto vary depending on the angle of the corner with maximum deflectionoccurring at approximately 90 degrees or more. The amount of offset atwhich the tangent arc 64 is printed is the same distance outward as thecompressed flowable bead 53 is displaced inward without compensation.Therefore, in the square corner, compression roller 59 pulls thecompensated, distorted corner back square during the process. In amore-rounded corner, the radius of curvature or amount of arc applied totangent arc 64 may vary as a function of the amount of direction changebeing compensated for during execution of the tool path. For example,the amount of direction change in the tool path may require additionalcompensation or adjustment in the amount of applied tangent arc 64. Insome aspects, tangent arc 64 may vary in shape, and/or in size,depending on the characteristics of the direction change beingcompensated for. Moreover, properties of flowable material 53 (e.g.,viscosity, density, curing or hardening time of the material, etc.)and/or the size, shape, or configuration of the bead of depositedflowable material 53 during operation of machine 1, may affect theamount of tangent arc, the position of tangent arc, the size of tangentarc, the shape of tangent arc, or other characteristics or combinationsof characteristics to be applied to the tool path. In some embodiments,one or more characteristics of tangent arc 64 applied may be the samefor each change in direction, regardless of the characteristics of thechange in direction. In other words, in some aspects, a standard tangentarc 64 may be added to the tool path prior to any change in directionthat meets or exceeds a threshold level.

With reference now to FIG. 5b , as compression roller 59 re-engagesflowable material 53, the previously created bulge 65 in the materialbead flow path is pulled inward toward the workpiece in the samedirection as the executed direction change. In doing so, tangent arc 64added to the tool path is cancelled out, and the layer of compressed,flowable material 53 (or bead) is restored to its intended path 66.Accordingly, inclusion of tangent arc 64 may reduce or eliminatedistortion 63 shown in FIG. 4c . As discussed above, tangent arc 64 maybe of any pre-determined configuration based on the intended path 66 ofa part to be formed.

FIG. 6 depicts an exemplary method of adding a tangent arc 64 to atool-path program. The exemplary method begins at starting point 67,and, at step 68, a tool-path program may be constructed for additivemanufacturing using suitable software, for example, CAD software. Thegenerated tool path may then be monitored for any directional changesincluded in the programmed tool path at step 69. This monitoring mayoccur during generation of the tool path, after generation of the toolpath, or during execution of the tool path by additive manufacturingmachine 1. The monitoring software used to analyze the generated toolpath program for directional changes may be the same as or separate fromthe software used to generate the tool path. In some aspects, CADsoftware may be used both to generate the tool path and to monitor thetool path for changes in directions. In some examples, a separate orindependent computer processing unit may be configured to detect, check,and/or analyze any changes in the direction of the tool path.

Next, if a directional change in the tool path is detected at a step 70,then at a step 71, the change in direction is assessed to determinewhether it exceeds a predetermined angle. In some examples, thispredetermined angle may range from approximately 40 degrees toapproximately 90 degrees. In some embodiments, the predetermined anglemay be adjustable, e.g., by software programming. If a change indirection of the tool path is not detected at step 70, then, at a step73, it is determined whether or not the tool path program has come to anend. If it has, the method stops. If the tool path program has notended, then the tool-path program continues to be checked for changes indirection at a step 75.

If the change in direction at a step 71 is determined to exceed thepredetermined threshold angle, then, at step 72, the monitoring softwareadds a tangent arc 64 to the tool path at a predetermined distance inadvance of the directional change. The added tangent arc 64 isconfigured to divert the tool path outward by a predetermined amount,creating an intentional outward bulge of the layer (or bead) ofcompressed, flowable material 53 that is deposited during execution ofthe tool path just before the change in direction. Once tangent arc 64is added to the tool path, the method returns to step 73 to determinewhether the tool path program has ended. If it has, the method stops andmonitoring of the tool path is complete. If the tool path program hasnot ended, then the tool-path program continues to be checked forchanges in direction at a step 75.

While steps 68-75 are depicted in a particular order, the principles ofthe present disclosure are not limited to the order depicted in FIG. 6.

While principles of the present disclosure are described herein withreference to illustrative embodiments for particular applications, itshould be understood that the disclosure is not limited thereto. Thosehaving ordinary skill in the art and access to the teachings providedherein will recognize additional modifications, applications,embodiments, and substitution of equivalents all fall within the scopeof the embodiments described herein. Accordingly, the inventionsdescribed herein are not to be considered as limited by the foregoingdescription.

We claim:
 1. An additive manufacturing method, comprising: generating atool path including a first direction and a second direction; assessingthe tool path to determine if a change in direction in the tool pathexceeds a predetermined angle; moving a nozzle of an applicator head inthe first direction, wherein the nozzle is configured to deposit aheated material, and wherein the applicator head includes a roller;diverting the nozzle along a tangent arc while depositing the heatedmaterial prior to a change in direction of the tool path to the seconddirection in order to compensate for the change in direction of the toolpath; and engaging the deposited heated material with the roller whilemoving the nozzle in the second direction of the tool path to move atleast a portion of the heated material deposited along the tangent arctoward the second direction, wherein the second direction is differentthan the first direction.
 2. The method of claim 1, wherein thepredetermined angle is within a range of approximately 40 degrees toapproximately 90 degrees.
 3. The method of claim 2, wherein theassessing occurs after generation of the tool path.
 4. The method ofclaim 1, wherein the tangent arc is formed in a direction opposite tothe change in direction of the tool path.
 5. The method of claim 1,further comprising moving the roller behind the nozzle to compress theheated material deposited by the nozzle.
 6. The method of claim 5,further comprising rotating the roller to a location opposite of thechange in direction of the tool path after the diverting and beforemoving the nozzle in the second direction.
 7. The method of claim 1,wherein the tangent arc is added to the tool path at a distance prior tothe change in direction, and wherein the distance is determined based onthe angle of the change in direction.
 8. The method of claim 1, whereina radius of curvature of the tangent arc is determined based on theangle of the change in direction.
 9. The method of claim 1, wherein theheated material deposited along the tangent arc includes an outersurface, and wherein the roller moves the outer surface away from thetangent arc and toward the second direction.
 10. An additivemanufacturing method, comprising: generating a tool path including afirst direction and a second direction; moving a nozzle of an applicatorhead in the first direction, wherein the nozzle is configured to deposita heated material, and wherein the applicator head includes a roller;diverting the nozzle along a tangent arc while depositing the heatedmaterial prior to a change in direction of the tool path to the seconddirection in order to compensate for the change in direction of the toolpath; and engaging the deposited heated material with the roller whilemoving the nozzle in the second direction of the tool path to move atleast a portion of the heated material deposited along the tangent arctoward the second direction, wherein the second direction is differentthan the first direction.
 11. The method of claim 10, further comprisingdetermining whether an angle of the change in direction of the tool pathexceeds a predetermined angle within a range of approximately 40 degreesto approximately 90 degrees.
 12. The method of claim 11, wherein thedetermining occurs after generation of the tool path.
 13. The method ofclaim 10, wherein the tangent arc is formed in a direction opposite tothe second direction of the tool path.
 14. The method of claim 10,further comprising moving the roller behind the nozzle to compress theheated material deposited by the nozzle.
 15. The method of claim 14,further comprising rotating the roller to a location opposite of thesecond direction of the tool path after the diverting and before movingthe nozzle in the second direction.
 16. The method of claim 10, whereinthe tangent arc is added to the tool path at a distance prior to thesecond direction, and wherein the distance is determined based on anangle of the change in direction.
 17. The method of claim 11, wherein aradius of curvature of the tangent arc is determined based on an angleof the change in direction.
 18. The method of claim 10, wherein theheated material deposited along the tangent arc includes an outersurface that forms a bulge, and wherein the roller moves the outersurface toward the second direction.